Harmonic drive motor

ABSTRACT

A core for a flexispline motor is enclosed within a distortable flexispline having the shape of an open tin can, such that under rest conditions the space between the flexispline and the core is constant. The core of the motor is shaped as in a hub and spoke configuration, with spokes having variable widths. Coils are fitted to the spokes and are connected in pairs such that pairs of coils on opposing spokes are in series bucking relationship. A second set of coils, which overlap the first coils, can be connected in a non-bucking manner to increase the magnetic flux produced by the coils on opposing spokes. The flexispline has a flexible ring gear incorporated in its surface near the open end which when magnetically attracted ceases to have a circular shape and forms a two-lobe (elliptical) or three-lobe shape. Under these conditions the corresponding points of the shape so formed contact a ring gear which is mounted on a rotating hub. The points of the flexible ring gear which correspond to the minor axes contact the surface of the core. As the magnetic force rotates the distorted shape rotates, but the flexispline itself does not rotate. Because the number of teeth on the ring gear and the flexible gear are different, the hub is forced to rotate at reduced speed. An alternative construction embodies a splined locking arrangement to rotatably fix an open cylinder, composite material flexispline to the electromagnetic core. Other concentric pairs of inner and outer electromagnetic winding arrangements achieve pull-in pull-out flexispline distortion of elliptical or threelobe shape.

This invention relates to a high torque low speed motor, which as partof its construction contains a electromagnetic permeable cup, which iselastically distorted by the influence of a electromagnetic field. Thiscup has the classical shape of an open-ended tin can in which a cylinderand generally an end disc are integrally connected. The open end of thecylinder incorporates a band gear having radially extending teeth, whichis also capable of undergoing elastic deformation as the cylinder of thecup is deformed. When the magnetically permeable cup is exposed to arotating magnetic field, an elastic distortion is produced, whichmanifests itself as a wave phenomena progressing around the open end ofthe cup. That is the open end of the can assumes the shape of an ellipse(two-lobed) or tricom (three-lobed), or (four-lobed) shape, whichcontinues to rotate about the longitudinal axis of the cup.

The open end of the cup on which the band gear is located is made tocontact a gear in close proximity to the cup (which gear does notundergo any significant distortion) and which is contacted by said gearfor example at two opposing points at the ends of the major axis of theelliptical shape assumed by the cup and band gear combination, or theprotruding nodes of the other shapes.

The band gear and the contacting gear have teeth, which mesh; both setsof teeth have the same pitch but differ in number. As the distortedshape of the end of the cup sweeps around the central axis of the cup,the radially extending teeth of the band gear progressively engagedifferent teeth of the contacting gear; and because of the differingnumber of teeth on the two gears, relative rotation of the two gearsoccurs. This gearing phenomenon is well known and is usually referred toas strain wave gearing.

An alternative form of construction embodies a composite materialsflexispline of open cylinder form, open both ends, and rotatively fixedby means of integral male longitudinal splines. These splines matinginto similar female splines formed in the circumferential surface of theinternal electromagnetic core, this allows band gear teeth radialmovement but prevents flexispline rotation, while permittingsignifigantly greater torque transfer with a low distributed pressure.This mating spline arrangement may also be applied beneficially to theone closed end cup construction of paragraph 1 above.

BACKGROUND OF THE INVENTION

The principles of strain wave gearing or flexispline drives are wellknown and are discussed in U.S. Pat. Nos. 2,906,143 (Sep. 29, 1959) and2,931,248 (Apr. 15, 1960) issued to Musser. There the underlyingprinciples involving the continuous oscillatory contact of a flexiblespline (flexispline) with a ring gear to produce a rotational outputfrom the ring gear are discussed in some detail. A torque is produced inthe ring gear by the continuous elastic deformation of the flexiblespline's gear tooth ring by a cam device called a strain inducer tocause the teeth on the flexispline to be driven into sequentialengagement with the teeth of the ring gear.

Because the fixed flexispline and the ring gear have a different numberof teeth, the ring gear is forced to rotate a distance equal to thesmall tooth difference (generally two teeth for elliptical distortion)between the flexispline and the ring gear for one revolution of thestrain inducer.

Providing that the number of teeth on the flexispline and ring gear islarge and the tooth differential is small between the flexispline andthe ring gear (as it usually is), a tremendous gear reduction ratio canbe realized between the rotation of the strain inducer and the ringgear. The output torque is developed from the continuous sequentialmeshing of the teeth of the flexispline with the ring gear and isproportional to the inverse of the gear ratio. This torque is generatedby the rotating strain inducer, which is constantly distorting theflexispline to engage the ring gear in a sequential manner.

Since 1959, a number of electromagnetically distorted strain wavegearing units have been produced in which a permeable magnetic cup wasdistorted by an electromagnetic force to produce rotation of theflexispline cup. Various materials, and configurations of the materials,forming the magnetic cup were attempted with varying degrees of success.Generally speaking, these devices have been limited to relatively lowoutput torque and power driving motors and stepping motors.

The size and shape of the unit may change, but the continuous sequentialmultiload distortion of a flexible cylinder is always present to produceoutput rotational motion at modified speeds and torques. It is a primeobjective of the present invention to extend the application of thiselectromagnetically driven flexispline technology into applicationsrequiring significantly greater and efficient output torque and power.

SUMMARY OF THE INVENTION

This invention relates to a low speed high torque motor, which containsas part of its construction a magnetically permeable sleeve(flexispline). Preferably, the sleeve in its non-deformed shape iscylindrical, but when under the influence of an electromagnetic fieldbecomes distorted into an multi-lobed shape. Both the flexispline andthe stator core of the motor remain rotationally stationary duringoperation of the unit.

The sleeve itself is preferably anchored to a cylindricalelectromagnetic core by means of a bolted flange arrangement orinterlocking splines, which facilitate torque transmission and preventrotation of the sleeve, but allow it to undergo a cross-sectional shapedistortion from a circle to the multi-lobed shape.

The electromagnetic core preferably is provided with a series of axiallyextending grooves (slots) on its surface which lock into complementarysplines on the inside of the surface of the flexispline sleeve. Thegrooves of this magnetic core may also house the stator windings whichproduce the electromagnetic field in the motor.

One part of the sleeve is provided with gear teeth which may beintegrally formed in the sleeve surface or it may be a band fixed to thesurface of the sleeve by some acceptable means. The band gear is alsodistorted by flexing motion of the sleeve to undergo the same distortionas the sleeve, and is preferably constructed from low elastic-modulusmaterials, such as polymer composite or hard coated magnesium oraluminium alloy.

The band gear of the sleeve meshes with another gear which, at rest,preferably is spaced very close to but not necessarily engaging the bandgear. The band gear and the enclosed gear have the same tooth pitch, butthe tooth number are deliberately made to be different for the twogears.

Upon excitation of the electromagnetic core, the sleeve undergoes wavedistortion as does the band gear and the distortion of the band gearcauses the band gear teeth to engage the teeth of the other gear atcorresponding points. As the distorted sleeve shape sweeps about theother gear, the tooth engagement progresses around the said gear andbecause of the difference in the number of teeth on the two gears, thesaid output gear rotates in greatly reduced motion, with respect to therotating excitation magnetic field.

The flexispline and the stator core comprise an electromagnetic systemfor which a rotating magnetic field is generally produced by a set ofpreferably inverted stator windings placed inside the flexispline whichin turn produces a magnetic flux to distort the flexispline. In thisinstance the stator windings are carried by the central core or thatpart of a conventional electric motor which is usually occupied by therotor. These stator windings may be formed using superconducting cooledwire such as provided by American Superconducting Corporation.

Preferably, the stator core comprises a body of laminated magneticmaterial or its equivalent to enhance the concentration of the magneticfield produced by a set of windings carried by the stator core.

These stator core windings are made to produce and concentrate arotating magnetic flux which preferably passes from the core, across anairgap, then into the flexispline, splits, and returns to the core. Thismagnetic flux preferably is produced by passing a programmed commutatedmodulated current through the core windings. The resultant magnetic fluxproduces a rotating concentrated radially directed force of variablespeed.

The stator core itself is preferably mounted on a sturdy stationarycentral post which may be hollow and comprised of an electricallyresistive (ohmic) magnetic material which serves to provide a rigidmounting means for the ring gear hub and any external load carried bythe hub at the end of the post. The hub is mounted on the post so thatthe ring gear provided in the hub enjoys a close concentric relationshipwith the stator core and the flexispline. Preferably, a set of thrustbearings assures that the coaxial relationship of the core and the ringgear is maintained during rotation of the hub.

The hub may be connected to an output shaft or a screw actuator toproduce rotational or linear motion. It may also be mounted within awheel of a vehicle to provide power to drive the wheel. When the deviceof this invention is mounted within a wheel, the shaft may also supportthe cantilevered vehicle load on the extended shaft and bearings. Thusreducing an equivalent parts count.

Some differences over the prior art may be noted.

-   1) The stator core is surrounded by the distorting flexispline, and-   2) The flexispline itself provides a return path for the magnetic    flux. This improves the applicability of this device to more diverse    applications and allows the flexispline diameter to be increased    substantially over the prior art motors. These features make it    possible to increase the output torque, power and efficiency of the    device over the prior art models.-   3) The flexispline itself does not rotate during operation of the    motor.-   4) The stator windings are designed to maximize the radially    directed force vector, which is responsible for causing engagement    of the band gear and the enclosed gear, and hence to maximise torque    output.-   5) The use of a composite or wire/tape wound under tension with    locked in radiat pressure over metal flexispline. Flexispline also    reduces flexispline distortion stiffness, which increases torque    output and efficiency. (Ref. Advance Mechanics of Materials seely.    Smith Wiley Page 608)-   6) The use of a splined interlocking flexispline arrangement    dispenses with the need for a closed-ended cup assembly to transfer    output torque, and/or reduces the torsional stiffness requirements    of same.-   7) The large diameter flexispline, allows flexispline distortion    with a reduced radially force, and permits more redially multi-lobed    distortion.-   8) The multi-lobed flexispline distortion capability, allows for    potential effective gear ratio change electromagnetically, on line    during operation.-   9) Rectangular profile cross section electromagnetic core teeth,    increase the radial force in a major way over dumbbell shaped teeth    employed in previous flexspline motor excitation systems.-   10) Variable with electromagnetic core teeth reduce the magnetic    flux saturation levels in the teeth thus increasing torque and power    output.-   11) Previous flexispline motor technology employed relatively thin    walled flexisplines of generally poor magnetic permanances the    present invention calls for relatively thick walled flexisplines(in    some cased ranging from 0.25 to 0.5 inches and greater as    required)of high magnetic permanence such as Carpenter Hypeco 15.-   12) The relatively thick walled flexispline of this invention    provides a major return path for the magnetic flux, thus maximizing    torque/power output.-   13) The preferred embodiment of this invention in terms of    flexispline and output ring gear orientation (interal teeth of    flexispline contacting output ring gear at point of radial force    application)as shown in FIG. 7 confersan approximate 10% advantage    over the alternative(external teeth on flexispline contacting ring    at 90° phase lag from point of radial force application) In terms of    flexispline diameterial deflection per unit radial force.-   14) The control circuitry and commutation strategy such as FIGS. 31    and 32 is ver important to the proper functioning of flexispline    motors specified in the paten application. However, there is no    present evidence that such have been applied before in the strain    motor context. Otherwise, the negative torque due to declining    inductance cancels out most of the positive torque due to increasing    inductance.

PRIOR ART

US Pat. No. 2,906,143 Musser Sep. 29 1959:

This patent describes in detail the principles of strain wave gearingusing a mechanical strain inducer to distort the flexispline. At FIGS.54 and 55 Musser briefly describes a method of operation of aflexispline device driven by a polyphase electrical input and a seriesof electrical solenoids.

U.S. Pat. No. 3,169,201 Spring et al Feb. 9, 1965:

This patent describes a flexispline motor having an external stator(which is stationary) comprising a number of circumferentiallydistributed salient poles (axially aligned solenoid pole pairs) havingan adjacent ring gear also mounted in the stator adjacent the poles.

A flexispline rotor is attached to a shaft and is mounted for rotationwithin the stator and is provided with extemal gear teeth on theexterior surface thereof to mesh with a ring gear encircling theflexispline. The flexispline rotor is provided with a radial series ofmagnetically permeable axially aligned laminations mounted under itssurface and allowed to pivot about one end (acting as a lever). Theselaminations are fastened to a rotor fulcrum ring and encouraged to pivotwhen subjected to a radial magnetic, force. A substantial mechanicaladvantage results. Upon actuation by a sequentially pulsed rotatingmagnetic field, the laminations pivot outwardly to cause the flexisplineto distort and contact the surrounding ring gear. This causes rotationof the flexispline rotor and its attached shaft (in a direction oppositethe direction of the rotating magnetic field). The rotor thus moves inaccordance with the tooth differential existing between the ring gearand the flexispline gear giving rise to substantially reduced rotationalmotion at the output.

U.S. Pat. No. 3,496,395 (Newell Feb. 17 1970):

In one described embodiment of this technology, a stator is suppliedwith a set of windings to produce a rotating magnetic field. The statorcomprises a series of stacked laminations which not only serve toprovide a mounting system for the windings but also serve to provide asurface for attaching a stationary co-axial ring gear in the air gapbetween the stator and the flexispline rotor. The stationary ring gearhas internally extending teeth which are engaged by the flexisplinerotor externally extending teeth as it is distorted by a rotatingmagnetic field.

The flexispline rotor in this instance is a thin (which limits themagnetic flux through it) flexible magnetically permeable hollowcylinder having ends closed by membranes which support and allowdeflection of the cylinder but limits the magnetic flux flow through it.

A shaft is made to pass through the central axis thereof. The closedends of the flexispline cylinder are fastened to the shaft so that anyrotation of the flexispline is transferred to the central shaft.

The rotating flexispline is provided with a gear which is mounted orformed in the surface thereof to contact the internally extending teethof the stationary ring gear.

The magnetic flux produced by the stator windings passes into andreturns from the hollow flexispline tube to produce a magneticattraction force. Thus the circular shape of the cylindrical flexisplinetube is distorted outwardly to force the teeth of the flexispline intoengagement with the teeth of the stationary ring gear. The flexisplinerotor thus rotates according to the tooth differential of the two setsof meshing gears, but in the opposite direction to the rotating magneticfield.

The major focus of this patent is to produce a biased coiledmagnetically permeable flat strip within the flexispline rotor toenhance the magnetic attraction between the flexispline and the statorand to reduce edge effect discontinuities which effect the positioncontrolaccuracy in a servomotor positioning application.

U.S. Pat. No. 3,169,202 Proctor et al Feb. 9, 1965:

This patent describes a flexispline motor having a fixed external statorin which conventional three phase induction windings and a stationaryring gear are mounted. A flexispline having pockets of powdered ironarranged beneath its surface, is influenced by a rotating magnetic fieldto distort under the attractive force of that field. This causesengagement of the flexispline gear with the stationary ring gear toproduce motion in accordance with the tooth differential of theflexispline gear and the ring gear.

Various rotor constructions are shown in this patent, all designed toenhance the magnetic force attraction produced in the rotor by themagnetic field.

U.S. Pat. No. 3,609,423 Spring Sep. 28,1971:

This patent proposes the use of a tapered coil of flat flexible magneticmaterial beneath the flexispline to enhance elasticity and magneticforce attraction of the flexispline. The magnetic material isstrategically slotted axially to decrease eddy current circulation.

U.S. Pat. No. 5,691,584 Nov. 25, 1997:

This patent is an excellent example of the state-of-the-art electricallydriven vehicle in which a drive motor is located within the wheel and isconnected through a double reduction gear transmission to produce a highdriving torque.

U.S. Pat. No. 5,600,191 Feb. 4, 1997:

This relatively recent patent describes a driving assembly for a wheelIn which low torque requirements are produced by an inside-out motorwhere the stator carries permanent magnets.

U.S. Pat. No. 4,389,586 Jun. 21, 1983:

This patent describes a driving arrangement for the wheel of a verylarge off-the-road vehicle. A DC motor drives the wheel through a doublereduction gear train.

LIST OF THE DRAWINGS

FIG. 1 is a cross sectional view of a flexispline motor.

FIG. 2 is a cross sectional view of alternative construction to FIG. 1.

FIG. 3 is an exploded perspective of view of the device of FIG. 1.

FIG. 4 is an exploded perspective view of the device of FIG. 2.

FIGS. 5A, 5B, 5C show the distortion of the flexispline of FIG. 1 as themagnetic field rotates.

FIGS. 6A, 6B, 6C show the distortion of the flexispline of FIG. 2 as themagnetic field rotates.

FIGS. 7, 8, 9, 10 show alternative constructions for flexispline motors.

FIG. 11 is a sectional view of a flexispline and core shown at 6-6 inFIG. 1 and FIG. 2.

FIG. 12 is an illustration of the flux flow of a conventional polyphasesinusoidally excited flexispline motor having internal and external coreassemblies, with dumbbell-shaped stator core teeth.

FIG. 13 shows a core punching component of a purposed flexispline motor,with straight stator core teeth, and concentrated magnetic flux

FIG. 14 shows a winding configuration for a core composed of thepunchings of FIG. 13.

FIG. 15 shows the flux pattern for a flexispline core similar to FIG.14.

FIG. 16 shows a typical current flow in the four phases of windingassembly shown in FIG. 14.

FIG. 17 is a representation of an eight legged magnetic core alternativeless expensive structure.

FIG. 18 is a perspective view of a winding shaped to fit over one of thecore legs of FIG. 17.

FIG. 19 is an illustration of the core of FIG. 17 fitted with the coilsof FIG. 18.

FIG. 20 is a simplified wiring circuit for the core of FIG. 17.

FIG. 21 shows the typical flux distribution for the wired core of FIG.20.

FIG. 22 shows an illustration of a double core switched reluctanceflexispline motor.

FIG. 23 shows a flexispline motor of a tricornal flexisplineconfiguration.

FIG. 24 shows the motor of FIG. 23 with one set of poles energized.

FIG. 25 shows the motor of FIG. 23 with a second set of poles energized.

FIG. 26 shows the motor of FIG. 23 with a third set of poles energized.

FIG. 27 shows a preferential wave form for current supplied to theexcitation poles of the motor of FIG. 23.

FIG. 28 is an exploded view of a splined flexispline motor.

FIG. 29 is a cross sectional view of the assembled motor of FIG. 28.

FIG. 30 shows an alternative flexispline motor arrangement, havingin-board bearings.

FIGS. 31A, 31B, 31C, 31D describe, in blockdiagram form, controlcircuitry adaptable for control of switched-reluctance versions offlexispline motors.

FIG. 32 describes the commutation strategy for the flexispline motors.

THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1 and 3 in which wheel motor 10 is shown as across section FIG. 1 and as an exploded view in FIG. 3. The motor 10 ismounted on base plate 12, which in this illustration is provided withfour threaded holes 14. The number of threaded holes depends on theapplication; there may be more or less holes 14 depending on therequired output. A sturdy post 16 (which is preferably hollow, magneticand of a high ohmic resistance) is mounted on base plate 12 so as toproject orthogonally therefrom.

Post 16 is provided with keyway 18 and wheel bearing mounting segment20. Post 16 terminates in a threaded end 22.

A somewhat cup-shaped flexible sleeve 24 (flexispline) is mounted onbase plate 12 between a pair of spacers 26 by means of screws 28 so thatit may not rotate. Sleeve 24 has a closed end 30 (which may be ofsomewhat heavier construction than the cylindrical upstanding portion32) which is integrally attached to end 30.

Sleeve 24 has an open end 34 remote from end 30. The end 30 offlexispline 24 has a locating hole 36 provided therein to guide theflexispline along post 16 during installation, and the opening 36 servesto centre and locate the flexispline 24 on base 12 so that the holes 38and 40 in the spacers 26 and end 30 of flexispline 24 may be easilyaligried with threaded holes 14 of base plate 12 for ease of assemblyand to maintain gearing tolerances.

The cylindrical upstanding portion 32 of flexispline 24 is provided withan external toothed gear 42 at or near the end 34 of flexispline 24. Theflexispline 24 (in this instance) is composed of a highly permeablemagnetic material having a high magnetic saturation level, as well asexhibiting a high resistance to eddy current circulation.

A suitable material for flexispline 24 for this application would beiron or iron alloys including steel silicon, nickel and/or cobaltalloys(such as Carpenter HyperCo 15). The cylindrical shell 32 ispurposely made to be readially distorted so that its usual shape (thatis to say, its undeformed and undistorted shape—which is a cylinder) maybe distorted to take on a multi-lobed shape(when compelled by themagnetic force to change from its normal shape).

The deflection of the wall 32 of the flexispline 24 may be determined bythe following equation:P=K.ΔD.t3.E/r3where

-   K=a constant-   ΔD=diametrical deflection of cup (approximately twice the gear tooth    height)-   P=radial distorting force-   L=axial length of the cup-   t=wall thickness-   E=flexural modulus (or composite flexural modulus)-   r=radius of sleeve    Thus the ratio (t/r)³

One of the characteristics which should be determined with respect tothe flexispline 24 before degree of deflection force is finallydetermined, is the amount of torsional twisting (shear stiffness) theflexispline 24 must withstand during operation (a function of the outputload torque). The spline (or band) gear 42 mounted or formed on theouter surface of the sleeve will have a significant influence on thesleeve stiffness, which should therefore be minimised. Equation (1)above will also apply to the presence of spline gear 42 on flexispline24 as well. In addition, it may be found that it is necessary to coatspline gear 42 with a hard coating to improve its wear characteristics,and to incorporate the interlocking splines of FIG. 28. This will reducetorque transmission shear requirements of the flexispline.

The flexispline 24 is mounted on base plate 12 by sliding it along post16 until holes 38 and 40 line up with threaded holes 14. Countersunkscrews 28 are threaded through holes 38 and 40 into the threaded holes14 to hold the flexispline 24 finely between spacers 26 against base 12.

Next a magnetic core 44 is slid into place on post 16 and is rigidlymounted and located on post 16 in its home position and held in thislocation (in this instance) by means of key 46 in keyway 18. Acorresponding keyway (not shown) is formed in core 44 to complement thekeyway 18 formed in post 16.

Core 44 is supplied with a winding 48 which is wound in core slots 50formed in the surface of core 44 in such a manner as to provide therotating magnetic field when energized. This field ultimately causes theflexure of the wall 32 of flexispline 24.

A switched reluctance motor type field winding (for example four phasetwo rotor pole, or six and three phase with three rotor poles) alongwith appropriate control circuitry and communtation, such as depicted inFIGS. 31 and 32, may be used to provide the necessary deflection of thesleeve 32 of flexispline 24. The field winding may also be comprised ofcooled superconducting wire as manufacture by American SuperconductorCorporation USA.

Next a hub 52 (on which a vehicle wheel.may be mounted) is rotatablyjournalled on post 16 by means of thrust bearings 54, 56 which aremounted on bearing segment 20 of post 16. In this instance, hub 52 is arobust casting having a similar shape to a truck or automobile wheel huband brake drum assembly.

Hub 52 is provided with a pair of bearing recesses to receive a pair ofthrust bearings 54 and 56 therein to assure that hub 52 is firmly lockedinto position and rotates concentrically with the axis of post 16.

Cylindrical shell 60 of hub 52 is provided with a cantilevered shellportion 62 which is provided with an internal spline gear 64. Gear 64 ismade to have teeth which mesh with the teeth of spline gear 42 offlexispline 24 but the teeth comprising gear 64 are intentionally madeto be different in number than the teeth in spline gear 42, but havingthe same pitch.

Hub 52 may be provided with a series of studs such as 66 for mounting awheel rim thereon.

Referring now to FIGS. 5A, 5B, 5C, and FIGS. 6A, 6B, 6C, motor 10 isrepresented in cross section as taken along the axis of post 16, showingthe distortion of flexispline 24 as the magnetic flux rotates about theaxis of motor 10. Note that core 44 and flexispline 24 are rotationallystationary, but gear 64 is forced to rotate in the same direction as therotating magnetic field.

The magnetic material comprising flexispline 24 is attracted to core 44at the points where the magnetic flux emanating from core 44 isgreatest. At a point lagging by 90° mechanical the interior surface offlexispline 24 is usually designed to be in close proximity to theexterior surface of core 44.

The rotating elliptical shape of flexispline 24 may in time produce wearon the surface of core 44 even though flexispline 28 and core 44 have norotational motion (both are stationary). Flexispline teeth 42 oscillatesabout their own axis with a very small amplitude.

Because of this it may be necessary to provide the contacting surfacesof flexispline 24 and core 44 with a lubrication, which may be in theform of a solid lubricant incorporated in the surface of core 44. Core44 may be fabricated from electrical iron laminations stacked to thedesired length, or core 44 may be a composite, having finely dividedparticles of a magnetic material encapsulated in a polymeric substance.The latter composite provides a material having good magneticpermeability characteristics, while providing excellent resistance tothe flow of three dimensional eddy currents. The composite core justdescribed also provides a surface in which it is quite possible toincorporate a solid lubricant to reduce frictional losses (which leadsto less production of heat in the core), and also to help dampen anyvibrations due to system resonances.

FIG. 2 shows the modification of the device of FIG. I wherein the ringgear (62 of FIG. 1) is equivalent to gear 162 located on the interior offlexispline 124. The core 144 is provided with winding 148 to providethe magnetic attraction of flexispline 124 toward core 144. The basicdifference in operation of the devices of FIGS. 1 and 2 is that theflexispline 24 of FIG. 1 contacts the ring gear 62 at an angle of 90°from the point of maximum flux force produced by core 44, whereas thepoint of contact of flexispline 124 (FIG. 2) with ring gear 162 iscoincident with the maximum flux force produced by winding 148 on core144 in FIG. 2. This results in approximately 10% reduction in requiredflexispline deflection force for the same defleciton.

FIGS. 4 and FIGS. 6A, 6B, 6C similarly describe the motor 110 of FIG. 2.

FIGS. 7 and 8 show an enhancement for the devices of FIGS. 1 & 2. Mostof the components of FIGS. 7 and 8 are identical to the components shownin FIG. 1 and FIG. 2.

A flexispline 244 is mounted on base 212. Core 244 carrying winding 248is mounted on post 216 and locked in place with key 246.

The major difference is the presence of a multi-layer wire and/ormetallic tape winding 280 on the surface of flexispline 224. Winding 280in this instance is shown having a circular cross section and is woundas a helix around flexispline 224. The winding 280 comprises a magneticmaterial to enhance the magnetic attraction of the flexispline 224 tocore 244, to minimize the generation of eddy currents, and to increaseflux flow area. In this context it is important to control the windingtension in such a manner so as to maximize the locked in radially stress(or pressure). This intern reduces the required flexispline distortionforce. An alternative means of achieving this locked in radially stressis to shrink fit a collar or band of magnetic material around the solidor wound flexispline. Other alternatives include band type clamps withappropriate choice of flexispline cylinder geometry and locked in radialstress iti is possible to approach the critical buckling stress of themultilayered wound cylinder with 2,3, or 4 modal (lobar) buckling modes.Thus reducing the required flexispline radial deflection force.

The winding 280 may be wound and bound to the surface of the flexisplineas in a filament winding process or as a preformed coil, which acts asthe flexispline. In either case the objective is to minimize thestiffness of the flexispline-coil combination (to keep the distortionsstiffness down to a acceptable level, whilst maximizing the area for theflow of magnetic flux).

To obtain a better fill factor and reduce the effect of radial air gapsin the wire layers, the wire comprising the winding 280 may have asquare or rectangular cross section. Suitable compositions for the wireor tape comprising winding 280 are; Carpenters silicone iron B, HyperCo15, or Honeywell amphorous metal 2605C0.

The turns of winding 280 should be insulated (preferably on the axialfacing only) from each other to reduce eddy current flow in winding 280,usually the polimar binding formed on the turns comprising winding 280is sufficient for this purpose. If not, an oxide or phosphate can beadded to same. Note that there is no electrical continuity between thewire layers because the, wire ends at both ends of the flexispline 224and thus forms an open circuit.

It may be expected that by the judicious selection of the magneticmaterial and the polymeric material binding the multilayer wire or tapeforming winding 280 of motor 210, that the distortion stiffness of thecombined metal flexispline 224 and winding 280 may be reduced by afactor of 3 or more in comparison with an equivalent solid metalflexispline. Similarly, increasing the helical wire-winding angle willalso reduce the distortion stiffness of the flexispline. In this contextit is important to control and lock in the winding tension in such amanner so as to maximise the locked in radial stress(or pressure), whichin turn reduces the required flexispline distortion force. Analtemativemeans of achieving this locked in radial stress is to shrink fit acollar or band of magnetic material around the solid or woundflexispline. Other alternatives include band type clamps. Withappropriate choice of flexispline cylinder geometry and locked in radialstress it is possible to approach the critical buckling stress of themultilayered wound cylinder with 2,3 or 4 modal (lobar) buckling modes.This reduces the required flexplined radial deflection force.

A flexispline motor 310, which is a modification of the flexisplinemotor 10 of FIG. 1, is shown having a composite cup 324 in FIG. 9. Thecup 324 is composed of a composite of magnetic powder filled polymer ora polymer bound wire or tape wound magnetic material bonded to flange345, which now functions as a torque transmission agent and fulcrum(lever pivot point) for the electromagnetic deflection of flexispline324. Alternatively, the open-ended flexispline cup concept of FIG. 28,29, 30. May be adapted.

A set of locking pads 370 and braking pads 372 are shown for arrestingmotion of the flexispline 324 and rotation of hub 352 if required.

In FIG. 10, a flexispline motor 410 is shown mounted on base 412. Aquill 416 is firmly mounted on base 412. A magnetic core 444 is securelymounted on quill 416 by means of key 446. Field excitation windings 448are wound on core 444.

The end 430 of flexispline 424 is firmly attached to baseplate 412 bymeans of spacers 426 and screws 428 as to be coaxial with quill 416 inits rest position. At the remote end 434 of flexispline 424 is a bandgear 442, which encircles the open end of flexispline 424 on theexterior surface thereof.

A driven element 452 is mounted in bearings 454 and 456 inside quill416. Driven element 452 comprises a disc 470 attached to shaft 472 whichextends through base 412 to form sharp projection 474, and disc 470 maycarry wheel studs such as 476 or a shaft extension such as 478 (in theabsence of studs 476).

This construction allows the flexispline motor 410 to be adaptable todrive a load from either or both ends simultaneously.

An overwrap winding similar to winding 280 may be incorporated into thestructure of flexispline 424 to improve its magnetic characteristics. Ofcourse, the motor structure may take the form of the flexispline motorin FIG. 2 wherein the flexispline 424 would surround the ring gear.

FIG. 11 is a representation of the Section 6-6 shown in FIG. 1. Theflexispline 24 is shown surrounding the core 44. Three windings 48 a, 48b and 48 c comprise winding 48. This is a three phase,sinusoidally-distributed, winding, which is a traditional winding. Thethree phase windings 48 a, 48 b and 48 c are distributed about the core44 in a well-known. manner. This winding, will serve to deflect theflexispline in the manner described previously. Variable speed andtorque control of this winding version can be achieved by means ofcommercially-available modified electronic A.C. induction-motorcontrollers. However, the resulting output power, torque and efficiencytend to be disappointing.

FIG. 12 shows the flux distribution for a flexispline motor having apolyphase two pole winding such as FIG. 11 excited by a sinusoidalsignal. The core 44 is surrounded by a flexispline 24 (and in thisinstance an additional flux return path is provided by outer cylindricalcore 45).

It is to be noted that the flux traverses the entire core 44 thus corelosses are inevitable where the flux passes in and through hub 47. Thewindings 48 a, 48 b, 48 c, have bulky end turns (which occupy aninordinate amount of space) at each end of the core 44. This also givesrise to substantial energy loss and heat generation in the stator coreand the end windings of 48 a, 48 b, 48 c. Additionally, the dumbbellshaped stator teeth significantly reduce the applied radial distortionforce. For these reason and other commutation problems, polyphaseexcitation winding are not the preferred embodiment for this invention.

It is proposed to use the core composed of stacked punchings such asthose illustrated in FIG. 8 to excite the flexispline for some of thealternative embodiments of this invention. FIG. 13 shows a core punching344 having an even number of core teeth but the teeth of the punchingare shown having variable widths. Core teeth 350, 352, 354, 356, 358,360, 362, and 364 each have two teeth such as 366 and 368 interspersedthere between. The core 344 is symmetrical in that this pattern isrepeated throughout the core 344.

FIG. 14 shows core 344 having a four phase 2 pole, reluctance motor typewinding wound thereon which will be excited by a switched D.C. 4 phaseexcitation having each phase separated by 45° mechanical.

Since the windings and core 344 are symmetrical, only one phase will bedescribed in detail. Tooth 352 is supplied with a winding 400 whichsurrounds only the tooth 352. Winding 400 is connected in a series.bucking relationship (to ensure opposite magnetic flux flow directions)with winding 402 on opposing tooth 360. These windings are energizedbetween terminals A-A1. A pair of windings 404 and 406 are wound on core344 to encompass teeth 368,352,370 and 384,360,386 respectively. Thesewindings are energized simultaneously with windings 400 and 402 toproduce more concentrated flux in the area of teeth 352 and 360.

The other three pole pairs are energized in 45 degree incrementssequentially to move the flux pattern around through 360° to cause awave deflection of the flexispline.

FIG. 15 shows the flux flow pattern for the coils 400, 404, 402 and 406on dumbbell shaped non variable width core teeth 352, 368, 370, 360, 384and 386 being fully energized with the coils surrounding teeth 350, 366,396, 380, 358 and 382 being partially energized. Note that the flux flowpattern is completely different from that illustrated in FIG. 12. Thegreatest concentration of flux is in teeth 352 and 360 which is shownlinking adjacent teeth 350 and 358 instead of passing through the corehub as shown in FIG. 12. Also, the dumbbell shaped core teeth reduce thepole tip magnetic flux density and thus reduce the applied flexisplinedelfection force in a major way. For these reasons variable widthstraight teeth are the preferred embodiment.

The energizing currept for the coils is illustrated schematically inFIG. 16. This current wave form is a switched DC current produced foreach set of pole pair windings such as 400, 404, 402, 406 which producesa gradual rotational distortion of the surrounding flexispline. Withoutthe overlap of the various phase currents in the windings of the core asshown in FIG. 16 the distortion of the flexispline tends to occur indiscrete steps. Additionally, this overlap (phase advance) has toincrease with increasing output rotational speed to compensate for thefield coil flux build up time constant. Of much greater importancehowever, is the current cut off point (current pulse trailing edge),when the field coil current reverses direction to discharge storedenergy this results in negative torque and the current must be cut off.The appropriate control strategy is shown in FIG. 32 resulting in atruncated current wave form. This control strategy is effected by thecircuitry of FIG. 31, accompanied by appropriate commutation signalsgenerated for instance by Hall effect devices.

The frequency and amplitude of the various currents should be controlledto adjust the speed and radial force of the distortion wave of theflexispline. Suitable circuitry in block diagram form adaptable toachieve such control is shown in FIGS. 31A, 31B, 31C, 31D (Ref. TexasInstrument Literature in BARA058 July 1977)

While windings such as 409, 402, 404, 406, etc., will function to causethe desired continuous wave distortion of the flexispline 24 of themotors 10, 110 and 210. However, there are some more less expensivewindings which are capable of producing the distortion of theflexispline with less input energy to the magnetic system, and areadaptable to 2, 3, or 4 lobe flexispline distortion.

FIG. 17 shows a magnetic core 524 for a flexispline motor applicationsuch as shown in FIGS. 1, 2, 7 and 8 in which the core is energized in acompletely different manner than the core coil system shown in FIG. 11.FIG. 17 represents a partial perspective of a core to be used in aSwitched Reluctance type Magnetic System. The core 524 comprises a hub526 and spokes 528 arranged in a spaced configuration comprising stacksof laminations to produce, in this instance, a magnetic core havingeight poles.

FIG. 18 shows a typical winding coil 530 for any of the legs 528 of thecore 524. Winding 530 is made to slip over the. selected leg 528 of core524. Each pole 528 is fitted with a formed coil such as 530. In allthere will be eight such coils 530 placed over the individual of thecore 524, for four or eight phase excitation, and two or fourflexispline rotor poles (similarly six coils/poles for three phaseexcitation with two or three rotor poles). Such arrangements allow thepotential for electromagnetic gear change ratio on the fly.

FIG. 19 shows the core 524 having coils 530 placed over each leg; notethe wiring sequence. Coil 530 which is placed on the ØA leg of core 524produces flux in the opposite direction as its series connected mateØA1. The actual winding configuration for 2 poles is shown moresimplistically in FIG. 20. Here the magnetic flux produced in legs ØAand the ØA1 is in direct opposition in the core. The remaining pairs ofthe six remaining poles are connected in pairs in a similar manner to ØAand ØA1. With each successive pole coil pair being wound in oppositemagnetic flux flow directions to the previous pair.

FIG. 21 is a representation of the flux produced in the four phaseswitched reluctance core 524. Note how the flux produced in the ØA andØA1 legs of core 524 is in direct opposition. The flux produced in theØA divides and splits to link the ØB and ØD1 legs. Similarly the fluxproduced in the ØA1 let splits and links the ØD leg and ØB1 leg. None ofthe flux produced in the ØA leg links the ØA1 leg as in the conventionalsinusoidally distributed winding illustrated in FIG. 11, thus reducingmagnetic flux saturation requirements. However it is obvious from FIG.21 that the flexispline thickness should be increased to accommodateflux flow similar to the core teeth.

Energization of the coils ØA, ØB, ØC, ØD is straightforward. Thecomplementary coils ØA and ØA1 are connected in series opposition, asare the balance of the coils. A four phase switched D.C. power supply istherefore required to produce a magnetic field which results in theproduction of a continuously moving distortion of the flexispline.The.power supply should have both magnitude and frequency control toproduce an output suitable for driving the flexispline motor forvariable speed operation. Along with appropriate commutation as shown inFIG. 32.

FIG. 22 shows a representation of a double core switched reluctance typeflexispline motor 600. Here an inner core 624 is provided with eightprotruding poles (similar to core 524) numbered 632, 634, 636, 638, 640,642, 644 and 646. Poles 632-646 are energized in exactly the same manneras poles ØA-ØD etc. of FIG. 19 with coils 648-660 being energized sothat the flux produced in opposing poles (such as 636 and 644) isbucking.

All the flexispline motors illustrated in FIGS. 1, 2, 7, 8, and 14 areprovided with a core contained within the flexispline itself. Theflexispline motor 600 is provided with an external core 670 which iscomposed of a series of stacked laminations which are formed into aunitary structure by techniques well known in the art. Core 670 isprovided with eight poles 672-686 which face poles 632-646. Poles672-686 are provided with coils 688-704. Flexispline 610 is mountedcoaxially with and midway between the poles 632-646 and 672 and 686.

When coils 648 and 656 produce flux in a series bucking relationship,coils 692 and 700 are simultaneously energized to produce a magneticpull (spaced 90° mechanically) on the flexispline 610 mounted betweenthe cores 624 and 670. The poles 692 and 700 are in space quadraturewith poles 648 and 656. While poles 648 and 656 pull the flexispline 610inwardly, poles 692 and 700 pull the flexispline outwardly to increasethe force of engagement of the flexispline 610 with its associated ringgear (not shown).

This arrangement also permits the coupling of a flexispline having 2sets of band gears, one on the inside, and one on the outside of theflexispline to engage an internal ring gear and an external ring gearsimultaneously. This would give rise to driving 2 loads with differentgear ratios.

The exterior core 670 should be securely mounted on a base (such as 12in FIG. 1) to hold the exterior core 670 in coaxial alignment withinterior core 624 and flexispline 610.

This arrangement will serve to increase the force of engagement of theflexispline and its associated ring gear. This double excitationarrangement will also function with the control strategy of FIG. 31 andFIG. 32. All that is required is an exterior core, the poles of whichproduce a magnetic field in space quadrature with the field produced bythe interior core 48. This provides the necessary distortion offlexispline 610.

FIG. 23 is a representation of a pull-pull flexispline motor having asix phase, three pole pull-pull type excitation, which is also capableof four or two pole excitation. The three pole version will now bedexcribed. Motor 800 is provided with a flexispline 810, and an innercore 824 having twelve protruding poles (similar to core 624) numbered846-868. Surrounding flexispline 810 is a stationary stator core 870having poles 872-894 protruding inwardly therefrom.

Poles 846-868 are provided with windings 896-918 and poles 872-894 areprovided with windings 920-942 respectively. At rest, as shown in FIG.23, the flexispline 810 assumes a round shape and the gear teeth (notshown) of flexispline 810 Which are integral with flexispline 810 do notengage the ring gear (not shown in FIG. 23). Thus at rest theflexispline 810 assumes a circular shape in the unexcited state.

FIG. 24 illustrates the resultant shaping of flexispline 810 when one ofthe four phases is energized.

Here inner poles 848, 856 and 864 are energized by windings 898, 906 and914 so as to deflect flexispline 810 inwardly, while outer poles 876,884 and 892 carrying windings 924, 932 and 940 respectively distort theflexispline outwardly to produge a tri-mode engagement with theflexispline 810 and. its ring gear or gears.

FIG. 25 shows the energization of the next phase when coils 900,908 and916 of inner poles 850, 858 and 866 are energized.

Simultaneously coils 926,934 and 942 on outer poles 878, 886 and 894 areenergized to move the distortion wave ahead 1 pole from that shown inFIG. 24.

FIG. 26 shows the energization of the six poles of the next phase andthe resulting distortions of the flexispline 810.

Thus the distortion of the flexispline moves through 120 space degreesfor the successive sequential energization of four poles. Energizationof the respective poles is provided by using chopped pulses of dc suchas shown in FIG. 27. Using the circuitry of FIG. 31, FIG. 32 andappropriate commutation signals. If the tooth differential between theflexispline and the ring gear (assume the ring gear is external to theflexispline) is 3, then for 1 complete excitation mode excursion through360 deg (space) there are 2 cycles of energization of each coil of themotor 800. This will advance the ring gear by 3 teeth during oneexcursion of the tricornal shape of the flexispline. In a flexisplinesuch as shown in FIGS. 1, 2, 7, 8 and 14 where the difference in teethbetween the flexispline and ring gear is two teeth, the ring gear wouldadvance only 2 teeth so that the tricornal shape lessens the gearreduction ratio.

Up to this juncture the various flexispline motors have generallyembodied a cup shaped flexispline arrangement (a cylinder with one endopen the other end closed). The main function of this cylinder is totransfer the full output load reaction torque from the band gear teeth42 (ref. FIG. 1) back to the base plate 12 (FIG. 1), in addition tofacilitating elliptical or tricornal distortion of same. This functionrequires the cylinder (flexispline) to possess adequate shear stiffness(thickness) in order to transfer the output load torque. This in turn,along with the closed cup end generally increases the flexisplinedistortion resistance, which in turn reduces output torque andefficiency. A new embodiment will now be described.

FIG. 28 shows the essential component parts of flexispline motor 10. Acore 12 is mounted in a frame (not shown) which prevents rotation ofcore 12. Core 12 may be composed of a stack of stamped laminations or itmay be a composite, cast of magnetic material. The core 12 is providedwith a shaft 15 having ends 14 and 16 at due opposite ends of core 12.Shaft end 14 is fixed so as to maintain core 12 stationary. Core 12 hasa series of protruding ribs 18 formed in the surface thereof separatedby valleys 20. The ribs 18 and the valleys 20 form a spline on which thesleeve type flexispline 22 is received in a spline engaging arrangement.The valleys 20 may also serve to house the windings necessary for theproduction of the electromagnetic field in the core.

Flexispline 22 which is of the form of a hollow cylinder has internalflexible ribs 24 (preferably of a polymeric based material) and valleys26 which mate with valleys 20 and ribs 18 of the core 10.

The fit between the flexispline 22 and the core is somewhat loose topermit the required flexing of the flexispline in a radial direction,but prevents motion of the flexispline 22 in a circumferentialdirection. Thus providing a reaction to the output load torque, but witha lower distributed surface pressure. (This technique can also be usedwith one closed end cup type flexispline)

An internal band gear 30 is fitted into one end of flexispline 22 so asto be integral therewith. The band may be bonded to the sleeve typeflexispline 22 or permanently fastened to the sleeve flexispline by someacceptable method.

It is important that the band gear 30 and the se eve type flexispline becapable of the required distortion in the presence of a rotatingmagnetic field established in core 12, in order to distort from acircular cross section to a multinodal shape in order to achieve properoperation of motor 10. Thus the use of construction materials having anelliptical low apparent elastic modulus for both the flexispline and theband gear is a necessity to achieve optimum operation of the motor 10.These techniques have been described previously in paragraphs [0055] to[0060].

FIG. 29 shows a cross section of the final assembly of motor 10. In thisFig., the shaft end 14 is permanently fixed to a reference to supportmotor 10. Shaft 14 is not permitted to turn. Coil windings 32 are shownon core 12 and are generally located in valleys (core slots) 20.

A fulcrum and retaining ring 34 is generally provided near the end ofsleeve type flexispline 22 to establish and stabilize the rest positionof the flexispline 22 on core 12.

A gear 36 is mounted on an assembly 38 for rotation on shaft 16 of motor10. Gear 36 has external teeth 40 to engage with the band gear teeth 42.The teeth 42 of band gear 30 do not necessarily engage the teeth 40 ofgear 36 under rest conditions.

The gear assembly 38 is mounted on bearings 44 for efficient rotation.Gear assembly 38 terminates in output shaft 46.

Core 12 is permanently fixed to the shaft 14-16 by means of key 50.

The motor functions as follows.

A rotating magnetic field is established in core 12 by windings 32. Themagnetic attraction established by the magnetic field in core 12attracts the magnetic sleeve type flexispline 22 so that opposite sidesof the flexispline are drawn inwardly so that band gear 30 contacts the40 of gear 36 at two diametrically opposed points.

As the magnetic field sweeps around the core 12 the distortion of theflexisplin e 22 and band gear 30 sweeps around gear 36 and core 12.

Because there are more teeth in the band gear 30 than the gear 36, thegear 36 rotates (according to the tooth differential) in a directionopposite to the rotating magnetic flux.

The ring 34 which may be fitted into sleeve 22 and core 12 by means of acircumferential groove and flange serves as a hinge, if desired for theflexure of the flexispline 22 on core 12 during operation.

The flexispline 22 may be made of a composite magnetic material, and orit may be a magnetic metallic cylinder over wound with a magnetic wireor magnetic tap contained therein to enhance its magneticcharacteristics while not increasing substantially to the stiffness ofthe sleeve. This contruction has been described previously.

Those skilled in the art will recognize that the motor 10 of FIG. 29 canbe reconfigured as the arrangement 101 of FIG. 30 to place the angularthrust roller bearings 44 inboard of the magnetic core 12, and to reducethe magnitude of any off-centred load. In this case the band gear 301 isplaced on the external surface of the flexispline 22, and the teeth 401are placed on the internal surface of gear 36. Also shown in FIG. 30 isthe potential placement of a rim 501, and tire 601, assembly fortraction vehicle applications, and in-wheel arrangements in particular.Elements of this arrangement are also applicable to the motors 10 (FIG.1), 110 (FIG. 2), 210 (FIG. 7), 210 (FIG. 8), 310 (FIG. 9), and 410(FIG. 10). It is also intended that some of the features of motors 10FIG. 29, and 101 FIG. 30 can be interchanged beneficially.

In summary, the flexispline motor of this invention preferably placesthe electro-magnetic core inside the flexispline, and minimises the fluxflow path and flexispline stiffness. This concentrates the radialdistortion force and maximizes the flexispline flux flow area. Thisconstruction has definite advantages over prior art devices in that themotor may produce greater torque and power and be much smaller and lesscomplicated than previous devices.

The torque and power efficiency produced by a flexispline motor dependsto a large extent on the square of the diameter of the flexispline. Inprior art devices the flexispline is surrounded by an electromagneticcore structure; and or motor casing, thus the diameter of theflexispline is much less than the external diameter of the motorstructure. The applicant's structure, generally places the flexisplineat the outer extremities of the motor thus increasing the torque versusmotor size ratio significantly, and reducing flexispline stiffness thusincreasing efficiency when compared to prior art motors.

The structure of the flexispline motor of this application is ideallysuited for applications such as traction motor, robot joint, and snowblower auger drives, because of compactness, requisite high torque atlow speed capability and the capacity to free wheel when the magneticcore is unexcited. Another application relates to hybrid automobiledrives, and particularly, in retrofit situations, by placing in-wheeldrives at the rear end of front wheel drive vehicles. Extension of thetechnology to large power dissipation devices is envisaged by means offorced cooling and the use of superconducting wire field windings, suchas that produced by American Super Conductor Corporation.

In another embodiment of this invention the flexispline motor places anelectromagnetic core both inside and outside of the flexispline, thisallowing tricomal distortion of same. This has an advantage insome,applications requiring smaller gear ratios and greater stiffness.

The Utilization of the composite flexispline embodying a magneticfilament or tape winding reduces the radial distortion stiffness whilstmaximizing the return path magnetic flux flow area. This improves thepower output by increasing the torque and improving the efficiency ofthe subject devices.

A comparison can be made between the commutation of the flexisplinemotor, and a switched-reluctance (SR) motor. It is recognised that thepoles in the flexispline motor can be regarded as equivalent to thepoles in an SR motor, and it is recognised that the commutation of aflexispline motor is similar enough to that of a SR motor, that theflexispline motor can take advantage of the modified existingwell-developed SR commutation technologies. FIGS. 31A, 31B, 31C, 31Dshow how the typical text-book manner of commutating a SR motor may beapplied to a flexispline motor. Whereas FIG. 32 depicts the commutationstrategy. This is achieved generally by means of Hall effect magneticsensing devices for rotor (flexispline) position and or parameticmeasurements of idle phase winding inductance as in FIG. 31D. Suchtechnology is an integral and necessary element for efficient operationof the flexispline motor of this patent specification.

In FIGS. 31A, 31B, 31C, the abbreviations are:

-   PI=proportional integral-   PID=proportional integral /derivative-   lfb=feed-back current-   lcmd=command current-   PWM=pulse width modulation-   DSP=digital signal processor

1. A flexispline motor comprising a cylindraceous electromagnetic core,a flexispline and rotatable hub means mounted on suitable support meansin a working relationship, said core being provided with a set ofsuitable windings to produce a commutated and controlled rotatingmagnetic field, a flexispline comprising a disc portion and cylindricalportion integrally joined together to form the general shape of an openended tin can mounted on said support means in such a manner that itencompasses said magnetic core and is in a coaxial relationship withsaid core, said cylindrically shaped portion of said flexisplinecomprising an elastically deformable magnetic material and being in aclosely spaced relationship with said core but not touching said core inan unexcited magnetic state, said flexispline having toothed externalgear means formed thereon in the form of an elastically deformable bandencircling the exterior surface of said cylinder generally near the openend of said flexispline, hub means mounted on said support meansadjacent to and coaxially with said flexispline, said hub havingcomplementary ring gear means overlying but closely spaced with saidgear means on said flexispline, wherein said open end of saidflexispline and said gear means being distorted in the presence of amagnetic field in said core to form a general multilobed shape such thatsaid gear means on said flexispline exhibits toothed engagement withsaid ring gear on said hub at the protruding lobes on the distortedshape so formed.
 2. A flexispline motor comprising a cylindraceouselectromagnetic core, a flexispline and rotatable hub means mounted onsuitable support means in a working relationship, said core beingprovided with a set of suitable windings to produce a commutatedrotating magnetic field, a flexispline comprising a disc portion andcylindrical portion integrally joined together to form the general shapeof an open ended tin can mounted on said support means in such a mannerthat it encompasses said electromagnetic core and is in a coaxialrelationship with said core, said cylindrically shaped portion of saidflexispline further comprising an elastically deformable magneticallypermeable material and being in a closely spaced relationship with saidcore but not touching said core in an unexcited magnetic state, saidflexispline having an elastically deformable toothed internal gear meansformed thereon on the interior surface of said cylinder in the form of aband, near the open end of said flexispline, hub means mounted on saidsupport means adjacent to and extending coaxially with said flexispline,said hub having complementary toothed gear means formed thereon at oneend thereof, said gear means being encircled by said elasticallydeformable toothed internal ring gear means of said flexispline, saidgear means and said internal ring gear being in closely spacedrelationship, but not touching in an unenergized magnetic state, whereinsaid internal ring gear being distorted upon the presence of a magneticfield in said core to assume a multilobed shape and contact said ringgear at the protruding lobes of the multilobed shape so formed.
 3. Aflexispline motor as claimed in claim I wherein said flexispline isoverwound with a magnetically permeable tape or as a helix of amagnetically permeable wire material with locked in radial stress orpressure.
 4. A flexispline motor as claimed in claim 2 wherein saidflexispline is overwound with a magnetically permeable tape or as ahelix of a magnetic wire material with locked in radial stress orpressure.
 5. A flexispline motor comprising a base, a hollow postaffixed to said base, a cylindraceous electromagnetic core and aflexispline mounted on said base and said hollow post so as to enjoy acoaxial working relationship with said hollow post, said core beingprovided with a set of suitable windings to produce a commutated andcontrolled rotating magnetic field, a flexispline comprising a discportion and cylindrical portion integrally joined together to form thegeneral shape of an open ended “tin can. mounted on said support meansin such a manner that it encompasses said magnetic core and is in acoaxial relationship with said core, said cylindrically shaped portionof said flexispline comprising an elastically deformable magneticallypermeable material and being in a closely spaced relationship with saidcore but not touching said core in an unexcited magnetic state, saidflexispline having toothed external gear means formed thereon in theform of an elastically deformable band encircling the exterior surfaceof said cylinder near the open end of said flexispline, shaft meansmounted within said post means on suitable bearings for rotation withinsaid post and passing through said base, said shaft means beingconnected to a disc shaped hub at an end opposite said base, ring gearmeans carried by said hub in a working relationship with saidflexispline, said ring gear means and flexispline gear.means having gearteeth that will mesh, but differ in number, wherein said open end ofsaid flexispline and said gear means being distorted in the presence ofa magnetic field in said core to form a general multilobed shape suchthat said gear means on said flexispline exhibits toothed engagementwith said ring gear on said hub at the protruding lobes on themultilobed shape so formed.
 6. A flexispline motor comprising a base,cylindraceous, electromagnetic core, a hollow post, a flexispline androtatable hub means mounted on a suitable shaft at a point intermediateits ends, said shaft means passing within said hollow post andcontrolled magnetic core and being supported on suitable bearing means,said shaft means being accessible at both ends of said motor, said corebeing provided with a set of suitable windings to produce a rotatingmagnetic field, a flexispline comprising a disc portion and cylindricalportion integrally joined together to form the general shape of an openended tin can mounted on support means in such a manner that itencompasses said electromagnetic core and is in a coaxial relationshipwith said core, said cylindrically shaped portion of said flexisplinecomprising an elastically deformable magnetically permeable material andbeing in a closely spaced relationship with said core but not touchingsaid core in an unexcited magnetic state, said flexispline having anelastically deformable toothed internal gear means formed thereon on theinterior surface of said cylinder in the form of a band, near the openend of said flexispline, hub means carrying a ring gear means mountedwithin said flexispline and extending coaxially with said flexispline,said ring gear means being encircled by said elastically deformabletoothed internal ring gear means of said flexispline, said gear meansand said internal ring gear having teeth which will mesh but differ innumber and being in closely spaced relationship, but not touching in anunenergized magnetic state, wherein said internal gear means beingdistorted upon the presence of a magnetic field in said core to assumean multilobed shape and contact said ring gear at the protruding lobesof the multilobed shape so formed.
 7. A flexispline motor as claimed inclaim 5 wherein said flexispline is overwound with a magneticallypermeable tape or with a helix of a magnetically permeable wire materialwith locked in radial pressure or stress.
 8. A flexispline motor asclaimed in claim 6 wherein said flexispline is overwound with amagnetically permeable tape or with a helix of a magnetically permeablewire material with locked in radial pressure or stress.
 9. Anelectromagnetic core for a flexispline comprising a magneticallypermeable core of a hub and spoke shaped construction, said corecomprising stacked laminations to form a unitary structure having aneven number of radially spaced rectangular profile poles surroundingsaid hub, a winding fitted to each pole to produce a magnetic field ineach pole, and the windings on each pair of opposing poles on said hubbeing energized to produce magnetic fields which oppose each other. 10.An electromagnetic core as claimed in claim 9 wherein the coils of eachpair of opposing poles on said hub are connected in a seriesrelationship.
 11. An electromagnetic core for the production of acontinuous wave deflection in a magnetically permeable flexisplinemember in a flexispline motor comprising, a series of stackedlaminations stacked together to form a unitary core having a hub andspoke configuration, such that an even number of rectangular profilecore legs extend radially from said core hub at evenly spaced intervals,each leg being supplied with suitable coil means, each coil beingsequentially energized from a suitable source of to electrical energy toproduce a rotating electrical field in said core, and wherein themagnetic forces produced in each opposing pair of core legs is in abucking relationship.
 12. An electromagnetic core as claimed in claim 13wherein the number of core legs is eight, and the source of electricalenergy is a four phase source having frequency, amplitude, andcommutation-control of the output current wave forms, and the coils oneach pair of opposing pairs of core legs is connected to said source ofelectrical energy in a series bucking relationship.
 13. Anelectromagnetic core for a flexispline motor said core comprising acircular configuration and having a series of radially extendingrectangular profile teeth protruding from said core, said teeth havingteeth of variable widths arranged in a regular sequence around thecircumference of said core separated by slots of uniform width.
 14. Anelectromagnetic core for a flexispline motor comprising a stack ofmagnetically permeable laminations arranged to form a substantiallycylindrical core, said core having a series of projecting rectangularshaped teeth having two distinct widths separated by slots of equalwidth, and wherein teeth of lesser width are double the number of theteeth of wider width.
 15. A winding system for the electromagnetic coreof claim 14 wherein each core tooth of wider width is provided with afirst coil and a secondary coil is made to encircle said first coil plusthe teeth of lesser width on either side of said core tooth of widerwidth.
 16. A flexispline motor comprising an electromagnetic core, aflexispline sleeve, and a gear device wherein: said core is mounted on astationary member and has the general shape of a cylinder having asplined exterior surface, said core having a set of windingsincorporated therein to produce a rotating magnetic field in said core,a magnetically permeable sleeve mounted coaxially on said core havingthe shape of a hollow cylinder having an interior cylindraceous surfacehaving a spline formed in said interior surface to mate with saidsplined exterior surface of said core in a sliding relationship whichpermits flexing in a radial direction and transfer of torque but whichdoes not permit said sleeve to move in a circumferential direction, saidsleeve having an overlapping end extending beyond said core, saidoverlapping end of said sleeve having an internal gear formed thereinhaving a predetermined tooth form of constant pitch, a driven gear beingmounted within said overlapping end of said sleeve in a coaxialrelationship with said core and said sleeve, wherein said driven gearhaving teeth which mesh with said internal gear and being mounted topermit rotation about a central axis of said sleeve and core, said gearand said sleeve being in a non contacting relationship in the absence ofa magnetic field in said core, wherein said sleeve undergoing a cyclicalelastic deformation in the presence of a rotating magnetic field in saidcore to form a multilobed shape such that the internal gear formed insaid sleeve contacts said driven gear in the presence of a rotatingmagnetic field in said core, such that the protruding ends of themultilobed shape so formed by said sleeve and internal gear contact saiddriven gear, to cause said driven gear to rotate.
 17. A flexisplinemotor comprising a magnetically permeable flexispline having the generalshape of an open tin can, having a predetermined radius r, saidflexispline having a set of gear teeth incorporated in a predeterminedsurface of said flexispline near the open end of said flexispline, saidflexispline being mounted coaxially within and between a pair ofsubstantially cylindrically extending magnetic core assemblies, an innercore assembly having a series of salient poles whose number is amultiple of three protruding therefrom so that the pole tips of saidinner core assembly lie in the locus of a circle having a radius r1, anouter core assembly having a series of inwardly extending poles equal innumber to the poles on said inner core assembly, such that each pole onsaid outer core assembly is spaced directly opposite from a pole on saidinner core assembly, the pole tips of said outer core assembly lie inthe locus of a circle having radius r2 such that r2 is greater than r isgreater than r1 winding means on said cores to establish two rotatingfields in space quadrature.
 18. A prime-mover apparatus, for convertingsupplied electrical energy into rotary mechanical motion of a rotor withrespect to a stator, about a drive-axis, wherein the stator comprises anelastically deformable magnetically permeable overwound with similarwire or metallic tape embodying a locked in radial stress or pressure;an annulus having gear teeth, which form a stator-drive-gear; theannulus is sufficiently elastic as to be deformable radially, beingdeformable in the sense that the annulus takes on a lobed configuration,upon appropriate radially-directed forces being applied to the annulus;the rotor is provided with gear teeth, which form a rotor-drive-gear;the rotor-drive-gear is a solid structure, not deformable to a lobedconfiguration; the rotor-drive-gear is concentric with thestator-drive-gear, and the number SGT of teeth on the stator-drive-gearis different from the number RGT of teeth on the rotor-drive-gear; thestator-drive-gear and the rotor-drive-gear are so configured that, whenthe thin-walled annulus of the stator has deformed to the lobedconfiguration, portions of the stator-drive-gear teeth corresponding tothe induced lobes of the annulus move radially into meshing engagementwith teeth of the rotor-drive-gear; the stator includes N electricalcoils, located at respective coil-orientations, around the drive-axis;in a manner such as to minimise the length of the magnetic flux flowpath. the coils are so structured, commutated, and arranged that, whenenergised with electricity, the coils create poles which exertrespective radially-directed magnetic forces in a programmed sequentialmanner. the arrangement of the apparatus is such that the saidradially-directed forces act upon the electrically deformed annulus, andinduce the annulus to deform into the lobed configuration; the apparatusincludes a commutator, for receiving the supplied electrical energy, andfor switching same to the coils, in a specialized manner therebyenergising and de-energising the coils, with the unused engerminus somelosses being returned to the energy source. the apparatus includes acyclic-operator, for operating the commutator for energising andde-energising the coils sequentially in an optimal rotational pattern,around the drive-axis; the arrangement of the apparatus is such thatoperating the commutator in the said rotational pattem is effective todrive the lobed configuration of the elastic stator annulus to rotatearound the drive-axis, its speed of rotation being a lobe-rotate-speedLRS rpm; whereby the rotor-drive-gear is driven to rotate at a speed ofLRS *(SGT-RGT)/SGT rpm; the electromagnetic core teeth on which thestator field winding is applied, embody a rectangular profile in axialplanform.
 19. The wire comprising the stator field winding of aflexispline motor is formed of hollow superconducting material.